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Abstract

Background

Testicular prosthesis has been applied clinically for decades, and implantation of
testis prosthesis under the tunica albuginea has been considered to be the standard
method in the most of the reports. However, postoperative scrotal appearance, the
mobilization and the palpitation of the prosthesis are not always satisfactory to
all the patients. Modifications in surgical techniques might be necessary to bring
improvements to the clinical outcomes in testicular prosthesis implantation.

Findings

In a group of 9 beagle dogs in this study, an orchiectomy succeeded with a testicular
prosthesis implantation under the tunica vaginalis, and a complete mechanical denudation
of the testicular parenchyma succeeded with an implantation under the tunica albuginea
were performed, respectively. Histopathological evaluations of the scrotal tissues
and the implants, which were made at the end of the follow-up, showed that all the
tested animals lived uneventful lives during the follow-up period, and no rejections
or infections were found. Prostheses implanted under the tunica vaginalis showed a
more satisfying mobilization and palpation than those implanted under the tunica albuginea.
Chronic inflammation in the para-prosthesis tissues with vascular proliferation and
fibrinogenesis were more common in the "under tunica albuginea" group than that in
the "under tunica vaginalis" group, although differences in fibrinogenesis between
the two groups were found to be statistically insignificant.

Conclusions

In this comparative study, we have re-evaluated the two most popular implantation
methods of testicular prosthesis, the "under the tunica albuginea" and the "under
the tunica vaginalis" pathways, in animal models. We found that the testicular prosthesis
were all well tolerated, but the prosthesis implanted under the tunica vaginalis showed
a more satisfying result concerning appearance, palpability, and histopathological
findings than that of the "under the tunica albuginea" group. The "under the tunica
vaginalis" method might become a more practical method for future testicular prosthesis
implantation.

Background

The psychological effect of castration secondary to the loss of testes as a result
of testicular trauma, cancer or spermatic cord torsion often results in negative impacts
to the lives of the patients. In the past, prostate cancer was once considered to
be rare in the Chinese population. Nowadays, the incidence of prostate cancer in the
Chinese population is increasing rapidly. As an alternative to surgical treatment
of prostate cancer, orchiectomy is often performed. In China, during the past several
decades, fewer demand for reconstruction of the "vacant" scrotum was actively requested
by these patients. With the social and economic changes in China, the demand for testicular
prosthesis is increasing rapidly now. However, postoperative pain still remains a
relatively common problem for the testicular prosthesis recipients. The relationship
between the surgical technique and the location of the prosthesis remains unclear.
In the present study, comparative observations concerning the effects of silicone
gel testicular prostheses implanted in different locations, "under the tunica albuginea"
or "under the tunica vaginalis", in Beagle dogs are reported.

Methods

The testicular prostheses used in the present study were a product of the Weining
Rubber Product Company (Shanghai, China). The prostheses consisted of two components,
silica gel as the filler, and silicon rubber as the shell. According to pre-operative
measurements of the testicles, the prostheses were manufactured in the range of 4.0
to 6.0 ml, and sterilized with ethylene oxide prior to use. The safety and biocompatibility
of the prosthesis has been tested in accordance with the institutional review board.

Overall, nine healthy adult male Beagle dogs were enrolled in the present study. The
study protocol was approved by the Institutional Ethical Committee.

Levels of serum testosterone, kidney function, and liver function of all the dogs
were tested before and after the implantation of testicular prosthesis.

Following intravenous administration of a mixture of Sumianxin II (Institute of Animal
Science, Changchun University of Agriculture and Animal Sciences) and ketamine (Shanghai
No.1 Biochemical Pharmaceutical Co., Ltd.) in a 1:1 ratio, a midline scrotal incision
was made in each side of the scrotum. For the left, a longitudinal incision in the
tunica albuginea was made, and the testicular parenchyma was carefully denuded bluntly
with a stainless steel scalpel holder. For homeostasis, the inner surface of the tunica
albuginea was gently pressed with gauze. For the right, a routine orchiectomy was
performed with the spermatic stump transfixed using silk suture.

A testicular prosthesis of appropriate size was implanted in different ways. For the
left, the prosthesis was placed under the tunica albuginea, and the tunica albuginea
was closed with an absorbable suture. For the right, the prosthesis was placed under
the tunica vaginalis. After these procedures, the scrotum was closed in multiple non-overlapping
layers with absorbable sutures. No drains were left in the surgical sites (Figure
1).

Figure 1.Illustration of surgical procedures regarding the implantation of the testicular prosthesis. For the left scrotum, the testicular prosthesis was placed under the tunica albuginea,
and for the right, under the tunica vaginalis.

NSAIDS (Indomethacin Suppositories, 25 mg) was given to the dogs every 12 hours in
the first 7 postoperative days. The animals were followed up for a period of 3 months,
and the testis together with the whole scrotum was removed en bloc at the end of the
observation. All the samples were preserved in 4% formaldehyde solution for later
histopathological evaluations.

Qualitative and quantitative evaluation under a standard light microscope for levels
of chronic inflammation and fibrosis were made according to the criteria below referring
to the Karademir's Method with appropriate modifications [1]:

Chronic Inflammation

The presence of plasmocytes, hystiocytes, lymphocytes as well as vascular proliferation
in the tissues around the prosthesis or testicle was graded from 0 to 3.

Fibrosis

The fibrohyalinization in the surrounding tissue was evaluated. All the parameters
were measured in 10 separate microscopic fields from different sites.

Grade I: Focal and mild fibroblastic activation.

Grade II: Diffuse mild fibroblastic activation.

Grade III: Significant fibroblastic activation.

For statistical evaluation, SPSS 16.0 software was used. Variables are presented as
mean ± SD. A Mann-Whitney U-test was utilized for data analysis and a level of p <
0.05 was considered to be statistically significant.

Results

During the follow-up of 3 months, all the nine research subjects survived uneventfully
with no apparent weight loss. Postoperative slight scrotal edema was found in both
side of the scrotum and lasted for 3 days and 7 days for the right and the left, respectively.
Rejection and infection were not found in any of the prosthesis-implanted dogs. In
all the dogs, the scrotal wounds healed within a week after surgery, and proliferative
scar or keloid tissue were not present. The testicular prostheses were mobile and
palpated at normal localizations in the right scrotum. However, in 7 out of the 9
dogs, prostheses in the left scrotum were found to be slightly asymmetric to and hanged
higher than that in the right. As for the palpation, the prosthesis in the left scrotum
seemed to be more rigid than that in the right.

The prostheses were removed en bloc together with the scrotal wall at the end of the
follow- up. All the prostheses were well enclosed by surrounding tissues, and no apparent
interspace was found between the tunica vaginalis and the tunica albuginea in the
left scrotum. No macroscopic leakage of the contents from the testicular prostheses
was identified. The prostheses could be easily detached from the tunica albuginea
or the tunica vaginalis.

Histopathological evaluations revealed that chronic inflammation and vascular proliferation
were present in both sides of the scrotum. These findings in the tunica albuginea
seemed to be more apparent in the left (Figure 2a), in contrast to that in the right (Figure 2b). The differences between the two sides were found to be significant with respect
to chronic inflammation, though it was insignificant as it comes to fibrosis. Fibrogenesis
in the surrounding tissues could also be found in both of the two sides (Table 1 and Table 2).

Figure 2.Chronic inflammation and fibrogenesis in the pseudo capsule of the testicular prosthesis. Magnification ×100 for each image, and ×200 for each corresponding oval inserted
image.

Before the surgery, the average serum testosterone of the dogs was 11.05 ± 1.85 nmol/L.
One week after implantation of the testicular prosthesis, it decreased to a level
of undetectable to the Radioimmunoassay (RIA) method. No significant differences with
respect to liver and kidney function were found between each paired group during the
follow-up (Table 3).

Discussion

Testicular prosthetic devices have been developed to restore the normal appearance
of the scrotum and hopefully to restore quality of life. The first testicular prosthetic
device was introduced in 1939 by Bowers using the metal alloy vitalium [2]. The practicality and safety of testicular prostheses has been tested clinically
for several decades, especially following the immergence of the silicone gel prosthesis
in the 1970s [3]. Despite the concerns over the relationship of silicone implants to connective tissue
disease [4-6], multispecialty expert panels in the United States (Institute of Medicine and the
National Science Panel) and the United Kingdom failed to find evidence which could
indicate any causal linkage between them. Silicone gel filled implants are currently
still widely used all over the world, especially in China [7].

For successful testicular prosthesis implantation, the key to the surgical procedure
is the correct positioning of the prosthesis in right location within the scrotum.
Surgically, the traditional inguinal procedure for testicular prosthesis implantation
has been applied for a long time, and has proven to be minimally successful in maintaining
the mobility and sensibility of the "testis". For this traditional method, there is
a possibility of inguinal migration of the prosthesis, spontaneous exit of the implant,
infection, hemorrhage, breakage of the implant, or persistent pains. With developments
in surgical techniques, testicular prosthesis implantation techniques have improved
greatly, and scrotal procedures with the testicular prosthesis implanted under the
tunica albuginea after denudation of the testicular parenchyma has been practiced
for many years. According to the literature, this technique has proven to be successful,
especially with regard to cosmetic appearance (mobility and sensibility, etc.) [8]. Despite these benefits, clinical observations have indicated that a postoperative
pain rate in 1% to 5%, or even to 9% can be found in the prosthesis recipients [9-11]. In the past, the majority of the recipients of testicular prosthesis in China were
those with unilateral or bilateral testicle loss from scrotum injuries, testicular
cancers, or testicular torsions. Nowadays, with the increasing incidence of prostate
cancer, the demand for testicular prosthesis implantation has also increased rapidly.
In our clinical practices, scrotal (under the tunica vaginalis) or subalbugenous (under
the tunica albuginea) implantation of the testicular prosthesis are the two most popular
surgical methods performed in this field. Despite a relative higher general satisfaction
rate to these procedures in most of the recipients, discomforts, especially postoperative
pains, have become a common problem. This phenomenon exposed the need for a comparative
re-evaluation between these two methods on a basis of scientific study. For a successful
testis prosthesis implantation, the recipient's satisfaction is a very important issue.
However, it is a subjective problem, and we could only get it from human recipients.
As for an intensive investigation, especially the histopathological study, we have
to use animal models. In fact, human recipients' satisfaction with their testis prosthesis
had been reported in a lot of literatures in the past. Because the focus of this study
is on those objective issues, such as the reasons for pains, asymmetric appearances,
and palpations, etc., so we decided to take an animal model.

In this perspective controlled animal study, a popular testicular prosthesis material,
silicone gel, is used to obviate the interference from prosthesis materials. In order
to maintain a relatively reasonable comparability, testicular prosthesis are implanted
in each side of the scrotum but at different locations, with one inside the scrotal
cavity (under the tunica vaginalis) after regular orchiectomy and another under the
tunica albuginea following denudation of the testicular parenchyma. During a follow-up
of 3 months, we found no incidence of infection, rejection or rupture of the implants,
and all the 9 dogs survived uneventfully. These results indicate the safety of the
silicone gel prosthesis utilized. Apparently, this is not a indicative of the superiority
of this testicular prosthesis to the materials used in other studies [12].

In animal experiments, one can not objectively quantify the subjective feelings of
recipient animals. However, postoperative scrotal appearances and histopathological
findings might provide useful information. In the present study, we found that in
7 out of the 9 animals, the bilateral scrotum were not symmetric, with the left "testicle"
in a relative higher position. On the one hand, we attribute this to the equal gravity
but unequal support to the prosthesis in the bilateral scrotum, where there is the
spermatic cord acts as a support for the left "testicle", but not for the right. On
the other hand, we speculate that the spontaneous contraction of smooth muscle in
the spermatic cord in the left might also play an important role. All these facts
naturally lead us to contemplate some deep initiative factors in behind. Histopathological
findings in our study revealed that slight to moderate inflammation and vascular proliferation
in the left scrotum are more common than that in the right throughout the entire follow-up
period of 3 months. According to these findings, we could naturally speculate that
chronic inflammation might act as a very important stimulating factor for the contraction
of the spermatic smooth muscles and thus the subsequent elevation of the left "testicle".
It could also be speculated that this might be a result of the denudation of the testicular
parenchyma, which could lead to edema and subsequent adhesion of the tunica albuginea
to the surrounding tissues.

In contrast to the left scrotum, chronic inflammation and fibrosis are relatively
slight in the right. Except for the lack of the denudation procedure of the testicular
parenchyma, the good elasticity and abundant blood supplies of the scrotal tissues
might help to alleviate the inflammation and provide a suitable accommodative environment
for the testicular prosthesis. All these findings imply that the presence of chronic
inflammation might even be the very cause of postoperative pains in the prosthesis
recipients. Recently, some researchers have reported that silicone could be used as
inducing materials in peritoneal cavity to produce a kind of mesothelium-lined fibroblast-rich
tissue for tissue-engineering purposes. These findings are indicative of a better
compatibility of silicone materials in peritoneal or scrotal tissues. In this study,
we have also found a thinner layer of mesothelium-lined fibroblast-rich tissues in
the inner surface of the false capsule in the right side [13].

Conclusions

In this comparative study, we have re-evaluated the two most popular implantation
methods of testicular prosthesis, the "under the tunica albuginea" and the "under
the tunica vaginalis" pathways, in animal models. From this study, we found that the
testicular prosthesis were all well tolerated, but the prosthesis implanted under
the tunica vaginalis showed a more satisfying result concerning with appearance, palpability,
and histopathological findings than that of the under the tunica albuginea group.
The "under the tunica vaginalis" method might be a more practical method for future
testicular prosthesis implantation.

Competing interests

The authors declare that they have no competing interests.

Authors' contributions

TLH and PC contributed equally to this manuscript. They designed, planned and performed
all the experiments, including surgical operations on the animals, the evaluation
of the pathological findings, and the writing of this manuscript. They all participated
in data analysis and figure generation, interpretation and writing of the manuscript.
All authors have read and approved the final version of the manuscript.